The revision of the lectures has been a task attended with no little
pleasure, especially since it has given the editor the opportunity for
an advance consideration of some of the more recent results, thus
materially facilitating investigations which have been in progress at
the New York Botanical Garden for some time. So far as the ground has
been covered the researches in question corroborate the conclusions of
de Vries in all important particulars. The preparation of the manuscript
for the printer has consisted chiefly in the adaptation of oral [xii]
discussions and demonstrations to a form suitable for permanent record,
together with certain other alterations which have been duly submitted
to the author. The original phraseology has been preserved as far as
possible. The editor wishes to acknowledge material assistance in this
work from Miss A.M. Vail, Librarian of the New York Botanical Garden.


D.T. MacDougal.
New York Botanical Garden, October, 1904.


PREFACE TO THE SECOND EDITION.

THE constantly increasing interest in all phases of evolution has made
necessary the preparation of a second edition of this book within a few
months after the first appeared. The opportunity has been used to
eliminate typographical errors, and to make alterations in the form of a
few sentences for the sake of clearness and smoothness. The subject
matter remains practically unchanged. An explanatory note has been added
on page 575 in order to avoid confusion as to the identity of some of
the plants which figure prominently in the experimental investigations
in Amsterdam and New York.